Krista Allen's scary encounter with a transient women who broke into her house and kicked her dog has made her to feel unsafe in her home ... and the poor pup's still suffering too.

Sources close to the "Baywatch" actress tell TMZ ... her 11-year-old Beagle Jack is dealing with a badly injured back, neck and front leg and had to have surgery Thursday. The good news -- he doesn't have broken bones and he's showing signs of progress since the operation ... but still has a long way to go.

We're told Krista's racked up between $5k - $10k in vet bills so far for Jack.

We broke the story ... Krista walked in on an intruder in February when she returned to her San Fernando Valley home and cornered the lady while she called 911. Our sources tell us Krista was cognizant enough to Google Translate on her phone to question the lady because she didn't speak English ... and that's how she determined her dog had been kicked.

And while Jack is now in recovery, it seems Krista's still reeling from the incident ... we're told she's moving out of her home because she no longer feels secure there after the intruder attack.